Pharmaceutical syringe piston

ABSTRACT

A piston to be provided within an inner wall of a barrel of a pharmaceutical syringe for dispensing medicament retained in the barrel is described. The piston includes a body defining a central face, a cylindrical portion, and an annular curved portion between the cylindrical portion and the central face portion. The piston also includes an inert film enclosing the central face portion and at least a part of the annular curved portion. The cylindrical portion and the part of the annular curved portion are together configured to maintain a fluid-tight seal with the inner wall of the barrel. A pharmaceutical syringe is described for dispensing a medicament includes a barrel configured to retain the medicament and the piston.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/354,675, filed Mar. 15, 2019, which is a continuation of U.S. patentapplication Ser. No. 14/758,042, filed Jun. 26, 2015, and issued as U.S.Pat. No. 10,258,744 on Apr. 16, 2019, which is a Section 371 ofInternational Patent App. No. PCT/US2013/035381, filed Apr. 5, 2013,which was published in the English language on Oct. 9, 2014 underInternational Patent Publication No. WO 2014/163645, the disclosures ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Embodiments of the present invention relate generally to apharmaceutical syringe piston, and more particularly, to apharmaceutical syringe piston with an improved inert film attachment.

U.S. Pat. No. 7,547,297 discloses a rubber syringe piston partiallyenclosed by an inert film in a cap-like manner. Specifically, the inertfilm is placed on an outer surface of a tapered face of the piston whichfaces the contents of a syringe. The inert film prevents contaminationof the medicament by materials leaching out of the stopper, andsimilarly prevents the medicament from penetrating the stopper duringextended storage periods, preserving the longevity of the stopper.

However, the film in U.S. Pat. No. 7,547,297 also extends along acylindrically-shaped portion of the piston. Applicant has discoveredthat, as a result of this configuration, the inert film abuts against aninterior wall of the syringe barrel. This arrangement can increase thebreakloose and extrusion (BLE) forces between the stopper and syringebarrel. Higher BLE forces can result in slippage or other errors duringinjection as the user applies greater pressure to the stopper in orderto expel the medicament. In addition, the film contact with the syringebarrel reduces the ability of the rubber material of the stopper tocreate a seal. The desired seal is at its highest quality when therubber directly contacts the inner surface of the syringe barrel.

It is desirable to provide a syringe piston that produces low BLE forceswith the inner surface of the syringe, and which creates an acceptableseal with the inner surface of the syringe, while still utilizing aninert film to prevent cross-contamination of the syringe piston materialwith the medicament.

BRIEF SUMMARY OF THE INVENTION

Briefly stated, a preferred embodiment of the present inventioncomprises a pharmaceutical syringe piston having a longitudinal axis andincludes a body having a central face portion oriented essentiallyperpendicularly with respect to the longitudinal axis of the piston. Thecentral face portion has a first outer circumference and a maximum firstdiameter measured perpendicularly to the longitudinal axis of thepiston. A cylindrical sealing portion proximate the central face portionand oriented coaxially with respect to the longitudinal axis of thepiston has a first axial end, a second axial end, and a wall extendingtherebetween. The wall has a second outer circumference and a seconddiameter measured perpendicularly to the longitudinal axis of thepiston. The second diameter is essentially constant along thelongitudinal axis between the first and second axial ends of thecylindrical sealing portion and is larger than the maximum firstdiameter of the central face portion. An annular curved portion, whichconnects the first axial end of the cylindrical sealing portion to thefirst outer circumference of the central face portion, has a maximumouter diameter less than the second diameter of the cylindrical sealingportion. An inert film encloses the central face portion and at least apart of the annular curved portion and has an outer boundary disposedbetween the first axial end of the cylindrical sealing portion and thefirst outer circumference of the central face portion.

Another embodiment of the present invention comprises a pharmaceuticalsyringe for dispensing medicament includes a barrel configured to retainthe medicament. The barrel has a longitudinal axis, an inner wallcoaxial with respect to the longitudinal axis, a first axial opening,and an opposing second axial opening. A piston body has opposing firstand second axial ends and is slidably disposed within the barrel. Thepiston body has a face portion at a first axial end thereof facing thefirst axial opening of the barrel. At least a portion of the faceportion is enclosed by an inert film having a first outer circumference.The piston body has a sealing portion proximate the face portion. Thesealing portion is cylindrically shaped and has a second outercircumference of a size sufficient to maintain the sealing portion incontact with the inner wall of the barrel. The sealing portion also hasan outer diameter that is essentially constant along the longitudinalaxis of the barrel. The sealing portion is in contact with the innerwall of the barrel at the second outer circumference of the sealingportion. The first outer circumference is smaller than the second outercircumference such that the inert film does not extend axially along anypart of the sealing portion.

Still another embodiment of the present invention comprises Apharmaceutical syringe piston having a longitudinal axis and includes abody having a face portion oriented essentially perpendicularly withrespect to the longitudinal axis of the piston, and a cylindricalsealing portion having a first axial end proximate the face portion, asecond axial end, a wall extending therebetween, and that is orientedcoaxially with respect to the longitudinal axis of the piston. The wallhas a first outer circumference and a first diameter measuredperpendicularly to the longitudinal axis of the piston and that isessentially constant along the longitudinal axis between the first andsecond axial ends of the cylindrical sealing portion. An inert filmencloses at least a portion of the face portion of the body such thatall of an outer surface of the inert film exposed on the piston bodylies transverse to the longitudinal axis.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofa preferred embodiment of the invention, will be better understood whenread in conjunction with the appended drawings. For the purpose ofillustrating the invention, there are shown in the drawings anembodiment which is presently preferred. It should be understood,however, that the invention is not limited to the precise arrangementsand instrumentalities shown.

In the drawings:

FIG. 1 is a partially sectioned side view of a pharmaceutical syringecontaining a piston body in accordance with a preferred embodiment ofthe present invention;

FIG. 2 is a side elevational view of the piston body of FIG. 1 ; and

FIG. 3 is a bottom side perspective view of the piston body of FIG. 1 .

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right,” “left,” “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “inwardly” and “outwardly” refer to directions toward and awayfrom, respectively, the geometric center of the piston and designatedparts thereof. Unless specifically set forth herein, the terms “a”, “an”and “the” are not limited to one element but instead should be read asmeaning “at least one”. The terminology includes the words noted above,derivatives thereof and words of similar import.

Referring to the drawings, wherein the same reference numerals are usedto designate the same components throughout the several figures, thereis shown in FIG. 1 a pharmaceutical syringe 10 for dispensing medicament(not shown) to a patient. The syringe 10 includes a preferablycylindrically-shaped hollow barrel 12 configured to retain themedicament. The barrel 12 may be made from glass, plastic, or the like,as is conventionally known. The barrel 12 preferably has a longitudinalaxis A, and an inner wall 14 that is coaxially disposed about thelongitudinal axis A.

The barrel 12 also includes a first axial opening 16 and an opposingsecond axial opening 18. The first axial opening 16 may be fitted to adelivery device (not shown), such as a conventional needle, transferdevice, or the like (not shown), for transporting the medicament fromthe barrel 12 to the patient. The second axial opening 18 is providedfor the receipt and movement of a longitudinally extending plunger shaft20. The plunger shaft 20 extends from a first axial end (not shown),through the second axial opening 18 of the barrel 12, to a second axialend 20 a. The first axial end of the plunger shaft 20 engages a pistonbody 22 slidably disposed within the barrel 12. The piston body 22 isformed substantially of a resilient material, such as rubber or similarelastomer.

Referring to FIGS. 2 and 3 , the piston body 22 includes opposing firstand second axial ends 22 a, 22 b and is coaxially disposed with respectto the longitudinal axis A of the barrel 12. The piston body 22 includesa face portion 23 at the first axial end 22 a thereof that is preferablyformed of a central face portion 24 and an annular curved portion 28.The central face portion 24 is preferably oriented essentiallyperpendicularly with respect to the longitudinal axis A and faces thefirst axial opening 16 of the barrel 12. In this manner, the centralface portion 24 is used to contact the medicament and force it throughthe first axial opening 16 of the barrel 12. The central face portion 24also preferably has a maximum diameter D_(F) measured perpendicularly tothe longitudinal axis A that defines an outer circumference of thecentral face portion 24. The central face portion 24 preferably has aconical shape, such that a center thereof is spaced apart from the outercircumference thereof along the longitudinal axis A. However, the shapeof the central face portion 24 is not so limited, and may also befrusto-conical, flat, rounded, or the like. The inner wall 14 of thebarrel 12 proximate the first axial opening 16 may be shaped tocomplement the shape of the central face portion 24 of the piston body22.

The piston body 22 further includes a sealing portion 26 proximate theface portion 23 which, when the piston body 22 is disposed within thebarrel 12, is in contact with the inner wall 14 of the barrel 12. Thesealing portion 26 preferably has a first axial end 26 a, a second axialend 26 b, and a wall 27 extending therebetween, which is preferablycylindrically shaped and lies along the longitudinal axis A of thesyringe 10 when the piston body 22 is disposed in the barrel 14. Thecylindrically shaped part of the sealing portion 26 preferably has adiameter D_(S), measured perpendicularly to the longitudinal axis A,that is essentially constant along the longitudinal axis A between thefirst and second axial ends 26 a, 26 b of the sealing portion 26, andwhich defines an outer circumference thereof to contact the inner wall14 of the barrel 12. This contact provides a fluid-tight seal to preventmedicament from seeping past the piston body 22 and toward the secondaxial opening 18. It is preferred that the maximum diameter D_(F) of thecentral face portion 24 is smaller than the diameter D_(S) of thesealing portion 26.

The maximum outer circumference of the central face portions 24 of thepiston body 22 may be connected to the first axial end 26 a of thesealing portion 26 by the annular curved portion 28 of the face portion23. Preferably, the curved portion 28 is outwardly convex in shape, asshown in FIG. 2 , such that the radius of curvature extends into thepiston body 22. However, other configurations may be used to connect theouter circumferences of the central face and sealing portions 24, 26,such as concave shapes (e.g., wherein the radius of curvature extendsaway from the piston body 22), multiple convex/concave curves, or thelike. The annular curved portion 28 preferably has an outer diameterthat is smaller than the diameter D_(S) of the sealing portion 26.

In preferred embodiments of the present invention, the central faceportion 24 and at least a portion of the annular curved portion 28 ofthe piston body 22 are enclosed by an inert film 30. The film 30 ispreferably made from a fluorinated polymer material, as is generallyknown. To avoid the disadvantages described above, the film 30preferably does not extend axially beyond the first axial end 26 a ofthe sealing portion 26 or along any part of the sealing section 26. Thatis, the film 30 is disposed coaxially with the longitudinal axis and hasan outer circumference that is smaller in size than the outercircumference of the sealing portion 26, which is sufficiently sized tomaintain contact of the sealing portion 26 of the piston body 22 withthe inner wall 14 of the barrel 12. Preferably, the outer boundary ofthe film 30 is disposed between the first axial end 26 a of thecylindrical sealing portion 26 and the outer circumference of thecentral face portion 24. As a result of this configuration, the outersurface of the inert film 30 that lies exposed on the piston body 22 istransverse to the longitudinal axis A. In this way, contact with theinner wall 14 by the inert film 30 is minimized while the criticalfunction of maintaining a contamination seal between the piston body 22and the drug in contact therewith.

It is preferred that the piston body 22 also include at least one, andmore preferably a plurality, of radially protruding stabilizing ribs 32that are disposed between the sealing portion 26 and the second axialend 22 b of the piston body 22. Each rib 32 includes a diameter DRmeasured perpendicularly to the longitudinal axis A and an outercircumference, each of which may be identical for each rib 32, as shownin FIGS. 1-3 . However, the circumference and diameter DR may differbetween ribs 32, as desired. It is preferred that the outercircumference and diameter DR of the ribs 32 are smaller than therespective outer circumference and diameter D_(S) of the sealing portion26 such that the ribs 32 have minimal contact with the inner wall 14 ofthe barrel 12. The ribs 32 are provided primarily for stabilizing thepiston body 22 within the syringe 10, although the ribs 32 may performsome sealing functions within the barrel 12, and it is desired to avoidadding unnecessary forces between the piston body 22 and the barrel 12.

The ribs 32 are preferably spaced apart along the longitudinal axis Afrom each other, and from the sealing portion 26 of the piston body 22,by one or more annular recesses 34, which are disposed between adjacentribs 32 and between the second axial end 26 b of the sealing portion 26and an adjacent rib 32. The diameter and circumference of the pistonbody 22 at each annular recess 34 may vary as necessary, as the materialof the piston body 22 within each recess 34 generally will not have muchinteraction with the overall syringe 10.

Toward the second axial end 22 b of the piston body 22 will be a trimedge 36, which is where the completed piston body 22 is separated from asheet (not shown) containing a plurality of piston bodies 22manufactured together as will be described in further detail below. Theouter circumference and diameter of the trim edge are preferably smallerthan the corresponding dimensions of the ribs 32 so as to have nointeraction with the inner wall 14 of the barrel 12. In addition, thetrim edge 36 does not need to be disposed as shown in FIGS. 1-3 , butmay instead be placed elsewhere on the piston body 22. Moreover, thetrim edge 36 may form one of the other components of the piston body 22,such as a rib 32, annular recess 34, the sealing portion 26, or thelike.

A receiving cavity 38 is formed from the second axial end 22 b of thepiston body 22 and extends longitudinally within the piston body 22. Thereceiving cavity 38 is configured to receive the first axial end of theplunger shaft 20. The receiving cavity 38 may be sized and dimensionedas appropriate to securely receive the plunger shaft 20, which ispreferably attached to the piston body 22 via a screw thread (notshown), although other connection types, such as friction orinterference fits, adhesives, welding, mechanical fasteners, and thelike may be used.

It is also preferred that at least a portion of the piston body 22 iscoated with a lubricant to further lower BLE forces between the pistonbody 22 and the inner wall 14 of the barrel 12. The lubricant furtherprevents the piston body 22 from sticking to the inner wall 14 duringthe injection process.

A process for manufacturing the piston body 22 will now be described.First, a non-vulcanized rubber sheet (not shown) together with afoil-like inert film (not shown) may be placed between die plates of aforming tool (not shown). The inert film, which is initially flat, canbe firmly joined with the rubber sheet. However, the film and rubbersheet may be introduced between the die plates independently from oneanother and placed loosely on top of each other. The rubber sheet isvulcanized under the influence of heat and pressure and isnon-detachably joined with the inert film. The forming tool forms theface portion 23, including the central face portion 24 and annularcurved portion 28, as well as the sealing portion 26 of the piston body22 in this first step.

The partially formed piston bodies 22 may thereafter be blanked out fromthe rubber sheet and placed into a second forming tool (not shown). Asecond non-vulcanized rubber sheet (not shown) is also placed into thesecond forming tool. Under the influence of heat and pressure, thesecond rubber sheet is vulcanized and molded to form the remainder ofthe piston body 22 to the second axial end 22 b, all of which is joinedto the sealing portion 26 at the second axial end 26 b thereof. Duringthis process, the receiving cavity 38 is also molded into the pistonbody 22 from the second axial end 22 b. Subsequently, the piston body 22is blanked out from the rubber sheet at the trim edge 36.

Although this is the preferred method for manufacturing the piston body22 in accordance with the present invention, other methods for theformation of a piston body 22 and the attachment of an inert film to thepiston body 22 may be used.

It will be appreciated by those skilled in the art that changes could bemade to the embodiment described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiment disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

What is claimed is:
 1. A syringe for dispensing a medicament, thesyringe comprising: a barrel configured to retain the medicament, thebarrel extending along a longitudinal axis of the syringe, the barreldefining an inner wall that is cylindrical and coaxial with respect tothe longitudinal axis, the inner wall defining an inner diameter of thebarrel; a piston provided within the inner wall of the barrel, thepiston comprising: a body defining: a central face portion orientedcoaxially with the longitudinal axis and defining a first pistondiameter measured perpendicularly to the longitudinal axis, wherein thefirst piston diameter is a maximum diameter of the central face portionand is less than the inner diameter of the barrel; a cylindrical portionoriented coaxially with the longitudinal axis, the cylindrical portiondefining a first axial end, a second axial end, and a wall extendingessentially along the longitudinal axis between the first axial end andsecond axial end, the wall defining a second piston diameter measuredperpendicularly to the longitudinal axis, the second piston diameter islarger than the inner diameter of the barrel; and an annular curvedportion between the first axial end of the cylindrical portion and thecentral face portion, the annular curved portion defining a curve, andan inert film enclosing the central face portion and at least a part ofthe annular curved portion, the inert film defining an outer boundary,and the inert film is configured to maintain a contamination sealbetween the body of the piston and the medicament retained in thebarrel, wherein the cylindrical portion and the part of the annularcurved portion together maintain a fluid-tight seal with the inner wallof the barrel and the outer boundary of the inert film is proximate to aleading-distal edge of the fluid-tight seal to minimize contact betweenthe inert film and the inner wall of the barrel.
 2. The syringe of claim1, wherein the fluid-tight seal defines a trailing-proximal edge at thesecond axial end of the cylindrical portion, and the fluid-tight seal iscontinuous between the leading-distal edge and the trailing-proximaledge.
 3. The syringe of claim 2, wherein the outer boundary of the inertfilm is disposed closer to the leading-distal edge of the fluid-tightseal than to the trailing-proximal edge of the fluid-tight seal.
 4. Thesyringe of claim 1, wherein the outer boundary of the inert film isadjacent to the leading-distal edge of the fluid-tight seal.
 5. Thesyringe of claim 1, further comprising a plunger shaft that extendslongitudinally and that is coupled to the second axial end of the bodyof the piston.
 6. The syringe of claim 5, wherein the second axial endof the body of the piston defines a receiving cavity configured toreceive an end of the plunger shaft.
 7. The syringe of claim 5, whereinthe plunger shaft extends through an axial opening of the barrel.
 8. Thesyringe of claim 1, wherein the curve defines at least one of a concaveshape with a radius of curvature that extends into the body or a convexshape with a radius of curvature that extends out away from the body. 9.A syringe for dispensing a medicament, the syringe comprising: a barrelconfigured to retain the medicament, the barrel extending along alongitudinal axis of the syringe, the barrel defining an inner wall thatis cylindrical and coaxial with respect to the longitudinal axis, theinner wall defining an inner diameter of the barrel; a piston providedwithin the inner wall of the barrel, the piston comprising: a bodydefining: a central face portion oriented coaxially with thelongitudinal axis and defining a first piston diameter measuredperpendicularly to the longitudinal axis, wherein the first pistondiameter is a maximum diameter of the central face portion and is lessthan the inner diameter of the barrel; a cylindrical portion orientedcoaxially with the longitudinal axis, the cylindrical portion defining afirst axial end, a second axial end, and a wall extending essentiallyalong the longitudinal axis between the first axial end and second axialend, the wall extends a distance along the longitudinal axis, the walldefining a second piston diameter measured perpendicularly to thelongitudinal axis, the second piston diameter is larger than the innerdiameter of the barrel, the wall contacts the inner wall of the barrelto maintain a fluid-tight seal with the inner wall of the barrel; and anannular curved portion between the first axial end of the cylindricalportion and the central face portion, the annular curved portiondefining: a first portion defining a curve and a diameter that is lessthan the second piston diameter, and a second portion with a diameterthat is substantially equal to the second piston diameter, the secondportion of the annular curved portion extends a distance along thelongitudinal axis, and an inert film enclosing the central face portionand at least a part of the annular curved portion, the inert filmdefining an outer boundary that does not extend axially beyond the firstaxial end of the cylindrical portion to minimize contact between theinert film and the inner wall of the barrel, wherein the distance thatthe wall of the cylindrical portion extends along the longitudinal axisis greater than the distance that the second portion of the annularcurved portion extends along the longitudinal axis.
 10. The syringe ofclaim 9, wherein the distance that the wall of the cylindrical portionextends along the longitudinal axis is at least twice as long as thedistance that the second portion of the cylindrical portion extendsalong the longitudinal axis.
 11. The syringe of claim 9, furthercomprising a plunger shaft that extends longitudinally and that iscoupled to the second axial end of the body of the piston.
 12. Thesyringe of claim 11, wherein the second axial end of the body of thepiston defines a receiving cavity configured to receive an end of theplunger shaft.
 13. The syringe of claim 11, wherein the plunger shaftextends through an axial opening of the barrel.
 14. The syringe of claim9, wherein the curve defines at least one of a concave shape with aradius of curvature that extends into the body or a convex shape with aradius of curvature that extends out away from the body.
 15. A pistonconfigured to be provided within an inner wall of a barrel of a syringefor dispensing medicament retained in the barrel, the piston comprising:a body defining: a central face portion oriented coaxially with respectto a longitudinal axis of the piston and defining a first pistondiameter measured perpendicularly to the longitudinal axis, wherein thefirst piston diameter is a maximum diameter of the central face portionand is less than an inner diameter of the inner wall of the barrel; acylindrical portion oriented coaxially with the longitudinal axis, thecylindrical portion defining a first axial end, a second axial end, anda wall extending essentially along the longitudinal axis between thefirst axial end and second axial end, the wall defining a second pistondiameter measured perpendicularly to the longitudinal axis, the secondpiston diameter is larger than the inner diameter of the barrel; and anannular curved portion between the first axial end of the cylindricalportion and the central face portion, the annular curved portiondefining a curve, and an inert film enclosing the central face portionand at least a part of the annular curved portion, the inert filmdefining an outer boundary, and the inert film is configured to maintaina contamination seal between the body of the piston and the medicamentretained in the barrel, wherein the cylindrical portion and the part ofthe annular curved portion are together configured to maintain afluid-tight seal with the inner wall of the barrel and the outerboundary of the inert film is configured to be proximate to aleading-distal edge of the fluid-tight seal to minimize contact betweenthe inert film and the inner wall of the barrel.
 16. The piston of claim15, wherein the fluid-tight seal defines a trailing-proximal edge at thesecond axial end of the cylindrical portion, and the fluid-tight seal iscontinuous between the leading-distal edge and the trailing-proximaledge.
 17. The piston of claim 16, wherein the outer boundary of theinert film is configured to be disposed closer to the leading-distaledge of the fluid-tight seal than to the trailing-proximal edge of thefluid-tight seal.
 18. The piston of claim 15, wherein the outer boundaryof the inert film is configured to be adjacent to the leading-distaledge of the fluid-tight seal.
 19. The piston of claim 15, wherein: thebody further defines a radially protruding stabilizing rib proximate thesecond axial end of the cylindrical portion and spaced apart from alongthe longitudinal axis of the piston, and the body includes an annularrecess disposed between the second axial end of the cylindrical portionand the radially protruding stabilizing rib.
 20. The piston of claim 19,wherein the radially protruding stabilizing rib defines a third pistondiameter, and the third piston diameter is less than the second pistondiameter.
 21. The piston of claim 15, wherein the body further defines:a plurality of radially protruding stabilizing ribs spaced apart fromthe second axial end of the cylindrical portion and from each otheralong the longitudinal axis; and a plurality of annular recesses,wherein each annular recess of the plurality of annular recesses isdisposed between two of the radially protruding stabilizing ribs. 22.The piston of claim 15, wherein the body comprises a resilient material,wherein at least a portion of the body is coated with a lubricant, andwherein the inert film comprises a fluorinated polymer material.
 23. Thesyringe of claim 15, wherein the curve defines at least one of a concaveshape with a radius of curvature that extends into the body or a convexshape with a radius of curvature that extends out away from the body.24. A piston configured to be provided within an inner wall of a barrelof a syringe for dispensing medicament retained in the barrel, thepiston comprising: a body defining: a central face portion orientedcoaxially with respect to a longitudinal axis of the piston and defininga first piston diameter measured perpendicularly to the longitudinalaxis, wherein the first piston diameter is a maximum diameter of thecentral face portion and is less than an inner diameter of the innerwall of the barrel; a cylindrical portion oriented coaxially with thelongitudinal axis, the cylindrical portion defining a first axial end, asecond axial end, and a wall extending essentially along thelongitudinal axis between the first axial end and second axial end, thewall extends a distance along the longitudinal axis, the wall defining asecond piston diameter measured perpendicularly to the longitudinalaxis, the second piston diameter is larger than the inner diameter ofthe barrel; and an annular curved portion between the first axial end ofthe cylindrical portion and the central face portion, the annular curvedportion defining: a first portion defining a curve and a diameter thatis less than the second piston diameter, and a second portion with adiameter that is substantially equal to the second piston diameter, thesecond portion of the annular curved portion extends a distance alongthe longitudinal axis, and an inert film enclosing the central faceportion and at least a part of the annular curved portion, the inertfilm defining an outer boundary that does not extend axially beyond thefirst axial end of the cylindrical portion to minimize contact betweenthe inert film and the inner wall of the barrel, wherein the distancethat the wall of the cylindrical portion extends along the longitudinalaxis is greater than the distance that the second portion of the annularcurved portion extends along the longitudinal axis.
 25. The piston ofclaim 24, wherein the distance that the wall of the cylindrical portionextends along the longitudinal axis is at least twice as long as thedistance that the second portion of the cylindrical portion extendsalong the longitudinal axis.
 26. The piston of claim 24, wherein: thebody further defines a radially protruding stabilizing rib proximate thesecond axial end of the cylindrical portion and spaced apart from alongthe longitudinal axis of the piston, and the body includes an annularrecess disposed between the second axial end of the cylindrical portionand the radially protruding stabilizing rib.
 27. The piston of claim 26,wherein the radially protruding stabilizing rib defines a third pistondiameter, and the third piston diameter is less than the second pistondiameter.
 28. The piston of claim 24, wherein the body further defines:a plurality of radially protruding stabilizing ribs spaced apart fromthe second axial end of the cylindrical portion and from each otheralong the longitudinal axis; and a plurality of annular recesses,wherein each annular recess of the plurality of annular recesses isdisposed between two of the radially protruding stabilizing ribs. 29.The piston of claim 24, wherein the body comprises a resilient material,wherein at least a portion of the body is coated with a lubricant, andwherein the inert film comprises a fluorinated polymer material.
 30. Thesyringe of claim 24, wherein the curve defines at least one of a concaveshape with a radius of curvature that extends into the body or a convexshape with a radius of curvature that extends out away from the body.